Color phosphor screen of the single gun variety



Jan. 2, 1968 M. A. TOMS 3,361,918

COLOR PHOSPHOR SCREEN OF THE SINGLE GUN VARIETY Filed Jan. 11, 1966 FIG. I

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INVENTOR MAURICE A. TOMS FIG. 5

United States Patent 3,361,918 COLOR PHOSPHOR SCREEN OF THE SINGLE GUN VARIETY Maurice A. Toms, Washington, DC. (40 Woodward Ave., Asheville, NC. 28806) Filed Jan. 11, 1966, Ser. No. 519,980 1 Claim. (Cl. 313-92) This application is a continuation-in-part of copending application Ser. No. 267,539, filed Mar. 25, 1963, entitled, Color Phosphor Screen of the Single Gun Variety.

This invention relates to screens for cathode ray tubes such as are used in television pictures of the polychrome variety, and is particularly concerned with an improvement on the type of screen shown in the US. patent issued to A. V. Bedford, No. 2,307,188, Jan. 5, 1943.

An object of this invention is to provide cathode ray tube screens whose color of fluorescence can be controlled electrically.

Another object of this invention is to provide a screen that is featherweight, and practically immune to physical shock, particularly one that is self-supporting, and will not sag from overheating.

A further object of this invention is to provide a screen that can be operated at low second anode potential, because of an efiicient removal of the spent electrons of the scanning beam from the viewing screen.

Another object is a black and white television, with an independent plug-in-color matrix.

Another object is a screen that can be easily manufactured on semi-automatic machines in any shape, or size desired.

Another object is a screen which, when provided with optional honeycombing, will prevent lateral light contamination, and provide superior black and white pictures.

The novel features of the present invention are set forth in particular in the claims. The invention itself, however, both as to its construction and operation will be best understood from the following description of a specific embodiment, when read in connection with the accompanying single sheet of drawings.

FIGURE 1 is a general view of a television set, incorporating the screen of the present invention, and shows that the screen is composed of parallel strips.

FIGURE 2 is a greatly enlarged fragmentary view of the screen in FIGURE 1 and shows that the strips are in abc color rotation.

FIGURE 3 shows a strip or thread in cross section as it might be seen from the face of the tube 10. There is a conducting coating on the surface of the strip 2 and a second coating 1 of an insulating material over the conducting coating. An adhesive coating and color code dye over the insulating coating is not shown. Phosphors 3 are placed within the thread and held together by a temporary binder, such as cellulose nitrate.

FIGURE 4 is a schematic view and shows that the threads of FIGURE 2 are connected electrically depending on the color content.

FIGURE 5 shows how the thread 4 when placed in a loom for weaving cloth can be separated as to color so transverse strips 5 can be inserted to connect together electrically threads of similar colors and at the same time short together the conducting coating on each side of each strip 2, FIGURE 3. An inflatable balloon 6 is holding the strips in a mold 7.

Summarized, very briefly, the Bedford patent places a varying potential on vertical conducting strips forming a television viewing screen. Each strip supports a phosphor of one color, red, green or blue. The strips are placed in abc order. Similar color strips are connected together electrically into a unit. There are three units, red, green 'ice and blue. These units are connected to What was an early substitute for the modern color matrix.

The strips are composed of a transparent conductor on which the color phosphors are placed. The transparency of the conductor allows the light from the glowing phosphor to reach the eye of the viewer.

The electrons of the scanning beam of the patent are attracted to the strips depending on the amount of positive charge the strips bear. A color picture results when the strips are charged in proper time sequence, and in intensity.

A semi-conductor is a material which is intermediate to the good conductors, such as metals, and insulators. They include transparent conductors. In the Bedford patent the light emitted by the phosphors must traverse the transparent conductors supporting the color phosphor.

The present invention improves over the Bedford construction in that a conducting strip is positioned on each side of each phosphor strip and these conductive strips or layers are shorted together, so they remain at the same potential. The conductor strips adjacent phosphors of similar color content are connected together, much in the manner of the Bedford patent.

Since there are three colors, three color units are formed, red, green and blue. These are connected to the red, green and blue terminals of the color matrix respectively. The matrix varies the potential on each unit, as the color picture content varies.

As just pointed out, in order to control the red, green and blue color information it is necessary to join similar color strips together electrically. There is a conducting coating on each side of each phosphor strip or thread 2, FIGURE 3. These are shorted together and joined to other strips of similar color.

These connections are accomplished by placing a plurality of thin conducting strips transversely across the screen at appropriately spaced intervals or near the top and bottom edges of the screen.

One easy method of doing this is illustrated in FIG- URE 5. The 400 triplets of the screen are placed in abc color rotation, and kept in alignment by the warf frames of an ordinary loom for weaving cloth. The loom is separating the thread into layers of different colors. An inflatable balloon 6 has pushed the parallel thread into a mold 7, and is holding it in position so the loom can separate the three colors into layers. This separation allows transverse conducting strips -1 to be placed, permanently, to separate and to connect together thread of similar color content, and also to short together the conductors on each side of each thread 2, FIGURE 3.

To assure good connection a conducting paste may be applied to the transverse strips and an insulating coating may be applied on the reverse side, to electrically separate the color layers. This is not shown.

After these transverse strips are in place, heat or chemicals are applied, bonding the strips into a screen unit so it can be removed. It is placed on a form that determines its final shape, and heat lamps evaporate the temporary cellulose nitrate binder. It is ready for testing for electrical continuity and for subsequent insertion in the glass envelope.

The phosphor containing thread can be manufactured by slitting into long strips or threads wide films or sheets of cellulose nitrate, containing either red, green, or blue phosphor particles.

Each side bears a conducting coating, and any other desired coatings. The threads are cut-off from the wide film so they have a slightly oblong cross section. This enables the loom to place them so the proper side faces the screen surface.

The number of threads covered by the scanning beam is not critical. The electrons of the beam are attracted to the strips in proportion to the positive potential each strip bears, following a constantly varying probability curve. (Bedford patent, figure 3.)

The diameter of the thread can be made to vary as the light emission of the phosphors within the thread.

The only known example of the prior art that places a conductor on each side of each strip is the US. Patent to A. P. Kruper et al., No. 2,875,375, Feb. 24, 1959. It involves the placement of a plate on each side of each strip, and connects all plates on one side of the strips to ground. A varying potential is placed on the plates of the ungrounded side and since electrons bear a negative charge they are attracted to the more positive plate. This lateral deflection occurs after the electrons have entered the physical limits of the plates. This is caused by the confinement of the electric field within the plates, they being of unlike potential.

The said deflection in the Kruper device must occur very suddenly and since the electrons have mass, a large potential difference is mandatory.

In the present invention like charges on each side of each strip make the electric field extend outward, all the way to the deflection coils. As a result the electrons of the scanning beam are gradually guided to the positive plates.

In the Kruper patent device, if a saturated red is presented by the material for display only a third of the electrons are available. The other two thirds strike green and blue plates and are deflected, and lost. This means low luminosity for saturated colors. In the present invention, all of the electrons are attracted to the plates bearing saturated color information, and none are lost. This makes bright pictures, and results in lower currents, capacitances, and second anode potential.

What is claimed and desired to be secured by the United States Letters Patent is:

1. In a cathode ray tube for displaying images composed of the three primary colors the combination comprising screen means having a surface for display,

said screen means including a plurality of strips of substantially rectangular cross-section having side and edge portions, each of said strips comprising a laminated structure having outer layers of conductive material forming the side portions and an inner layer of a phosphor, means electric-ally short-circuiting said outer layers of conductive material on each strip, said strips being assembled in such fashion that the screen surface is formed by the edge portions of the strips, means insulating adjacent strips from each other, means electrically connecting every third strip to form three groups of strips representing the primary colors, electron beam generating means, means for applying biasing potential to each of said groups of strips, whereby the electrons will be attracted to the group or groups of strips having a positive potential applied thereby activating the inner phosphor layers to produce the desired image, said three groups of strips being biased at a rate greater than the persistence rate of said screen so that a composite image simulating the desired natural color is produced.

References Cited UNITED STATES PATENTS 2,307,188 1/1943 Bedford 31392 2,446,440 8/ 1948 Swedlund 31392 2,498,705 2/1950 Parker 31392 2,841,742 7/1958 Zalocha 3152l 2,875,375 2/1959 Kruper et al 31521 JAMES W. LAWRENCE, Primary Examiner.

DAVID J. GALVIN, Examiner.

R. JUDD, Assistant Examiner. 

1. IN A CATHODE RAY TUBE FOR DISPLAYING IMAGES COMPOSED OF THE THREE PRIMARY COLORS THE COMBINATION COMPRISING SCREEN MEANS HAVING A SURFACE FOR DISPLAY, SAID SCREEN MEANS INCLUDING A PLURALITY OF STRIPS OF SUBSTANTIALLY RECTANGULAR CROSS-SECTION HAVING SIDE AND EDGE PORTIONS, EACH OF SAID STRIPS COMPRISING A LAMINATED STRUCTURE HAVING OUTER LAYERS OF CONDUCTIVE MATERIAL FORMING THE SIDE PORTIONS AND AN INNER LAYER OF A PHOSPHOR, MEANS ELECTRICALLY SHORT-CIRCUITING SAID OUTER LAYERS OF CONDUCTIVE MATERIAL ON EACH STRIP, SAID STRIPS BEING ASSEMBLED IN SUCH FASHION THAT THE SCREEN SURFACE IS FORMED BY THE EDGE PORTIONS OF THE STRIPS, MEANS INSULATING ADJACENT STRIPS FROM EACH OTHER, MEANS ELECTRICALLY CONNECTING EVERY THIRD STRIP TO FORM THREE GROUPS OF STRIPS REPRESENTING THE PRIMARY COLORS, ELECTRON BEAM GENERATING MEANS, MEANS FOR APPLYING BIASING POTENTIAL TO EACH OF SAID GROUPS OF STRIPS, WHEREBY THE ELECTRONS WILL BE ATTRACTED TO THE GROUP OR GROUPS OF STRIPS HAVING A POSITIVE POTENTIAL APPLIED THEREBY ACTIVATING THE INNER PHOSPHOR LAYERS TO PRODUCE THE DESIRED IMAGE, SAID THREE GROUPS OF STRIPS BEING BIASED AT A RATE GREATER THAN THE PERSISTENCE RATE OF SAID SCREEN SO THAT A COMPOSITE IMAGE SIMULATING THE DESIRED NATURAL COLOR IS PRODUCED. 